[clang] [llvm] [clang-tools-extra] Add clang-tidy check to suggest replacement of conditional statement with std::min/std::max (PR #77816)

[Piotr Zegar via llvm-commits]

================
@@ -0,0 +1,240 @@
+//===--- UseStdMinMaxCheck.cpp - clang-tidy -------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "UseStdMinMaxCheck.h"
+#include "../utils/ASTUtils.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Preprocessor.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang::tidy::readability {
+
+static bool isImplicitCastType(const clang::CastKind castKind) {
+  switch (castKind) {
+  case clang::CK_CPointerToObjCPointerCast:
+  case clang::CK_BlockPointerToObjCPointerCast:
+  case clang::CK_BitCast:
+  case clang::CK_AnyPointerToBlockPointerCast:
+  case clang::CK_NullToMemberPointer:
+  case clang::CK_NullToPointer:
+  case clang::CK_IntegralToPointer:
+  case clang::CK_PointerToIntegral:
+  case clang::CK_IntegralCast:
+  case clang::CK_BooleanToSignedIntegral:
+  case clang::CK_IntegralToFloating:
+  case clang::CK_FloatingToIntegral:
+  case clang::CK_FloatingCast:
+  case clang::CK_ObjCObjectLValueCast:
+  case clang::CK_FloatingRealToComplex:
+  case clang::CK_FloatingComplexToReal:
+  case clang::CK_FloatingComplexCast:
+  case clang::CK_FloatingComplexToIntegralComplex:
+  case clang::CK_IntegralRealToComplex:
+  case clang::CK_IntegralComplexToReal:
+  case clang::CK_IntegralComplexCast:
+  case clang::CK_IntegralComplexToFloatingComplex:
+  case clang::CK_FloatingToFixedPoint:
+  case clang::CK_FixedPointToFloating:
+  case clang::CK_FixedPointCast:
+  case clang::CK_FixedPointToIntegral:
+  case clang::CK_IntegralToFixedPoint:
+  case clang::CK_MatrixCast:
+  case clang::CK_PointerToBoolean:
+  case clang::CK_IntegralToBoolean:
+  case clang::CK_FloatingToBoolean:
+  case clang::CK_MemberPointerToBoolean:
+  case clang::CK_FloatingComplexToBoolean:
+  case clang::CK_IntegralComplexToBoolean:
+  case clang::CK_UserDefinedConversion:
+    return true;
+  default:
+    return false;
+  }
+}
+
+class ExprVisitor : public clang::RecursiveASTVisitor<ExprVisitor> {
+public:
+  bool visitStmt(const clang::Stmt *S, bool &found,
+                 clang::QualType &GlobalImplicitCastType) {
+
+    if (isa<clang::ImplicitCastExpr>(S) && !found) {
+      const auto CastKind = cast<clang::ImplicitCastExpr>(S)->getCastKind();
+      if (isImplicitCastType(CastKind)) {
+        found = true;
+        const clang::ImplicitCastExpr *ImplicitCast =
+            cast<clang::ImplicitCastExpr>(S);
+        GlobalImplicitCastType = ImplicitCast->getType();
+        // Stop visiting children.
+        return false;
+      }
+    }
+    // Continue visiting children.
+    for (const clang::Stmt *Child : S->children()) {
+      if (Child) {
+        this->visitStmt(Child, found, GlobalImplicitCastType);
+      }
+    }
+
+    return true; // Continue visiting other nodes.
+  }
+};
+
+static const llvm::StringRef AlgorithmHeader("<algorithm>");
+
+static bool minCondition(const BinaryOperator::Opcode Op, const Expr *CondLhs,
+                         const Expr *CondRhs, const Expr *AssignLhs,
+                         const Expr *AssignRhs, const ASTContext &Context) {
+  if ((Op == BO_LT || Op == BO_LE) &&
+      (tidy::utils::areStatementsIdentical(CondLhs, AssignRhs, Context) &&
+       tidy::utils::areStatementsIdentical(CondRhs, AssignLhs, Context)))
+    return true;
+
+  if ((Op == BO_GT || Op == BO_GE) &&
+      (tidy::utils::areStatementsIdentical(CondLhs, AssignLhs, Context) &&
+       tidy::utils::areStatementsIdentical(CondRhs, AssignRhs, Context)))
+    return true;
+
+  return false;
+}
+
+static bool maxCondition(const BinaryOperator::Opcode Op, const Expr *CondLhs,
+                         const Expr *CondRhs, const Expr *AssignLhs,
+                         const Expr *AssignRhs, const ASTContext &Context) {
+  if ((Op == BO_LT || Op == BO_LE) &&
+      (tidy::utils::areStatementsIdentical(CondLhs, AssignLhs, Context) &&
+       tidy::utils::areStatementsIdentical(CondRhs, AssignRhs, Context)))
+    return true;
+
+  if ((Op == BO_GT || Op == BO_GE) &&
+      (tidy::utils::areStatementsIdentical(CondLhs, AssignRhs, Context) &&
+       tidy::utils::areStatementsIdentical(CondRhs, AssignLhs, Context)))
+    return true;
+
+  return false;
+}
+
+static std::string createReplacement(const BinaryOperator::Opcode Op,
+                                     const Expr *CondLhs, const Expr *CondRhs,
+                                     const Expr *AssignLhs,
+                                     const SourceManager &Source,
+                                     const LangOptions &LO,
+                                     StringRef FunctionName, const IfStmt *If) {
+  const llvm::StringRef CondLhsStr = Lexer::getSourceText(
+      Source.getExpansionRange(CondLhs->getSourceRange()), Source, LO);
+  const llvm::StringRef CondRhsStr = Lexer::getSourceText(
+      Source.getExpansionRange(CondRhs->getSourceRange()), Source, LO);
+  const llvm::StringRef AssignLhsStr = Lexer::getSourceText(
+      Source.getExpansionRange(AssignLhs->getSourceRange()), Source, LO);
+
+  bool IsImplicitCastTypeNeeded = false;
+  clang::QualType GlobalImplicitCastType;
+  if ((CondLhs->getType()->getUnqualifiedDesugaredType() !=
+       CondRhs->getType()->getUnqualifiedDesugaredType()) &&
+      (CondLhs->getType().getCanonicalType() !=
+       (CondRhs->getType().getCanonicalType()))) {
----------------
PiotrZSL wrote:

```
if (CondLhs->getType().getCanonicalType().getNonReferenceType().getUnqualifiedType() != 
    CondRhs->getType().getCanonicalType().getNonReferenceType().getUnqualifiedType())
```
Should be sufficient.

https://github.com/llvm/llvm-project/pull/77816